testcases/MORX-24.html

<?xml version="1.0" encoding="UTF-8"?>
<html xmlns:ft="https://github.com/OpenType/fonttest"
      xmlns:xlink="http://www.w3.org/1999/xlink">
<body>
<h3 id="MORX-24">MORX-24: Contextual Glyph Subsitution Forever</h3>

<div class="desc">
  The <a href="../fonts/TestMORXTwentyfour.ttf">font</a> for this
  test case attempts to run a denial-of-service attack on the
  rendering engine under test. The font’s finite-state transducer
  substitutes glyph <em>A</em> by <em>B</em>, <em>B</em> by <em>C</em>,
  <em>C</em> by <em>D</em>, <em>D</em> by <em>E</em>,
  and <em>E</em> by <em>A</em>. These transitions are all marked with
  the <em>DontAdvance</em> flag, so the machine never makes progress.
</div>

<div class="desc">
  If your rendering system is immune to this attack, it will detect
  getting stuck (for example, by imposing an upper limit on the number
  of transitions taken by the finite-state machine), and give up quickly.
  See <a href="https://github.com/foliojs/fontkit/issues/175">fontkit
  bug 175</a>.
</div>

<table>
  <tr>
    <th class="conformance-header">Conformance</th>
    <td class="should-not-crash" ft:id="MORX-24/1" ft:render="ABCDE"
        ft:font="TestMORXTwentyfour.ttf"/>
  </tr>
</table>

</body>
</html>